Conventionally, a ship (inboard boat) in which power is transmitted from a prime motor (engine) provided inside a hull to a forward-backward propeller provided outside the hull through a switching clutch and a propeller shaft has been known. A ship with a side thruster for a lateral movement in a rightward or leftward direction to improve the maneuverability at the time of landing or the like has also been known. The side thruster is formed of a propeller provided near the lateral center on the bow side to produce thrust in the left-and-right direction. The side thruster enables a ship to move in the left-and-right direction, thereby facilitating a landing operation.
When positioning the hull of a ship having the above configuration, it is necessary to steer the ship in consideration of mutual influence between the side thruster and the forward-backward propeller, and thus a steering operation of the ship is complicated. In view of this, a ship in which the side thruster and the forward-backward propeller are controlled in conjunction with each other by using a joystick lever to facilitate the steering operation has been known. See Patent Document 1, for example.
When the ship according to Patent Document 1 is to be positioned at a target position designated by using a GPS device and a heading sensor, the hull of the ship cannot be settled at the target position due to water current, wind, and the like, or an inertial force (way of the ship), thereby causing in frequent on and off operations of a driving device. In addition, in the case where a dead zone is provided around the target position to give flexibility in determining the position of the ship, the ship may be drifted by wind or water current and positioned on a boundary of the dead zone.